In "The Will to Believe," William James argues that you do not choose your beliefs. You believe that Abraham Lincoln existed, and if someone asks you to stop believing this, you cannot do so. He goes on to discuss Pascal's wager: the idea that one ought to believe in God, since one has everything to gain if this belief is true, and nothing to lose if it is false. There are several problems with this idea. You might, for instance, pick the wrong religion and be condemned by one of the gods in whom you did not believe. However, the most obvious problem is that you cannot force yourself to believe something against your will. You either believe in God (or a god), or you do not.

The analogy with Abraham Lincoln is an interesting one. The main reason why everyone believes that Lincoln existed is that there is a mass of historical evidence that he did. In the case of a more shadowy figure, like Robin Hood or King Arthur, opinion is divided. In such cases, the question cannot be answered with certainty by intellect alone, and so an element of choice enters into the matter. James regards both belief and disbelief as reasonable in such cases.

It is for you to decide whether you agree with James, and how much evidence is sufficient for you to believe or disbelieve in God. However, it is also important to consider that a lack of belief does not necessarily entail a commitment to disbelief. You might admit that you are not sure whether God exists, but decide to act as though he does while waiting for revelation. Equally, you might see God as an ideal, which exists intellectually and spiritually even if not literally.